Process for preparing polycarbonates using nitrogen crown-cyclic compounds as catalysts

ABSTRACT

An interfacial polymerization process for preparing a high molecular weight aromatic carbonate polymer by reacting a dihydric phenol with a carbonate precursor in the presence of a catalytic amount of a nitrogen-containing crown-cyclic compound.

This invention is directed to an interfacial polymerization process forpreparing high molecular weight aromatic polycarbonates which comprisesreacting under interfacial polycarbonate-forming conditions a dihydricphenol and a carbonate precursor in the presence of a catalytic amountof a nitrogen crown-cyclic compound.

BACKGROUND OF THE INVENTION

Polycarbonates are well known thermoplastic materials finding a widerange of uses, particularly for injection molding applications and asglazing sheet for replacement of window glass. The interfacialpolymerization technique, which is one of the methods employed inpreparing a polycarbonate, involves reacting a dihydric phenol and acarbonate precursor in the presence of an aqueous caustic solutioncontaining an alkali or alkaline earth metal hydroxide, and an inertorganic solvent medium which is a solvent for the polycarbonate as it isformed. While the interfacial polymerization process is generallyeffective in producing polycarbonates, it does, in general, suffer fromtwo disadvantages. Firstly, the rate of reaction is relatively slow.Secondly, there is a general difficulty in producing high molecularweight aromatic polycarbonates, i.e., those having a weight averagemolecular weight of about 15,000 to greater. Many techniques, such asthose employing ultrasonic waves during the reaction, have been employedto remedy these two disadvantages. These techniques have not alwaysproved to be entirely effective and involve the use of cumbersome andexpensive equipment. It is advantageous economically to speed up thereaction and to produce high molecular weight aromatic polycarbonateswithout having to employ extra equipment or more severe reactionconditions. One such method is the use of catalysts in the interfacialpolymerization process.

However, there is generally relatively little known about effectivecatalysis of polycarbonate reactions. The prior art discloses thatcertain compounds such as tertiary and quaternary amines and their salts(U.S. Pat. No. 3,275,601), guanidine compounds (U.S. Pat. No.3,763,099), and ammonia and ammonium compounds (U.S. Pat. No. 4,055,544)are effective catalysts for the interfacial polymerization process forproducing polycarbonates. However, the prior art also teaches thatcertain organic nitrogen compounds function as molecular weightregulators or chain terminators in the polycarbonate reactions. Thus,the afore-mentioned U.S. Pat. No. 3,275,601 discloses that aniline andmethyl aniline function as chain terminators in the polycarbonatereaction, while U.S. Pat. No. 4,001,184 discloses that primary andsecondary amines are effective molecular weight regulators. Furthermore,U.S. Pat. No. 4,111,910 teaches that ammonia, ammonium compounds,primary amines, and secondary amines function as chain terminators inthe formation of polycarbonates via the interfacial polymerizationprocess, and U.S. Pat. No. 3,223,678 teaches that monoethanolamine andmorpholine act to break the polycarbonate chain thereby resulting inlower molecular weight polycarbonates.

DESCRIPTION OF THE INVENTION

This invention is directed to an interfacial polymerization process forproducing high molecular weight aromatic carbonate polymers wherein adihydric phenol is reacted with a carbonate precursor in the presence ofan aqueous caustic solution containing an alkali metal or alkaline earthmetal hydroxide and a catalyst which is a nitrogen-containingcrown-cyclic compound.

The reaction of a dihydric phenol such as2,2-bis(4-hydroxyphenyl)propane with a carbonate precursor such asphosgene results in a high molecular weight aromatic polycarbonatepolymer consisting of dihydric phenol derived units bonded to oneanother through carbonate linkages. The reaction is carried out in thepresence of an aqueous caustic solution containing the alkali andalkaline earth metal hydroxide as acid acceptors and an inert organicsolvent medium which is a solvent for the polycarbonate as it is formed.Generally, a molecular weight regulator is also present to control themolecular weight of the polycarbonate polymer. In the process of thepresent invention, a nitrogen containing crown-cyclic compound ispresent and acts as an effective catalyst to speed up the reactionbetween the carbonate precursor and the dihydric phenol.

The high molecular weight aromatic carbonate polymers produced inaccordance with the practice of this invention include carbonatehomopolymers of dihydric phenols or carbonate copolymers of two or moredifferent dihydric phenols. Additionally, the production of highmolecular weight thermoplastic randomly branched polycarbonates andcopolyester-polycarbonates are included within the scope of thisinvention. The randomly branched polycarbonates are prepared bycoreacting a polyfunctional organic compound with the afore-describeddihydric phenol and carbonate precursor.

The dihydric phenols employed in the practice of this invention areknown dihydric phenols in which the sole reactive groups are the twophenolic hydroxyl groups. Some of these are represented by the generalformula ##STR1## wherein A is a divalent hydrocarbon radical containing1-15 carbon atoms, --S--, --S--S--, ##STR2## X is indepently hydrogen,halogen, or a monovalent hydrocarbon radical such as an alkyl group of1-4 carbons, an aryl group of 6-10 carbons such as phenyl, tolyl, xylyl,naphthyl, an oxyalkyl group of 1-4 carbons or an oxyaryl group of 6-10carbons and n is 0 or 1.

Typical of some of the dihydric phenols that can be employed in thepractice of the present invention are bisphenols such asbis(4-hydroxyphenyl)methane, 2,2-bis(4-hydroxyphenyl)propane (also knownas bisphenol-A), 2,2-bis(4-hydroxy-3-methylphenyl)propane,4,4-bis(4-hydroxyphenyl)heptane,2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane,2,2-bis(4-hydroxy-3,5-dibromophenyl)propane, etc.; dihydric phenolethers such as bis(4-hydroxyphenyl)ether,bis(3,5-dichloro-4-hydroxyphenyl)ether, etc.; dihydroxydiphenyls such asp,p'-dihydroxydiphenyl, 3,3'-dichloro-4,4'-dihydroxydiphenyl, etc.;dihydroxyaryl sulfones such as bis(4-hydroxyphenyl)sulfone,bis(3,5-dimethyl-4-hydroxyphenyl)sulfone, etc., dihydroxy benzenes,resorcinol, hydroquinone, halo- and alkyl-substituted dihydroxy benzenessuch as 1,4-dihydroxy-2,5-dichlorobenzene,1,4-dihydroxy-3-methylbenzene, etc., and dihydroxy diphenyl sulfides andsulfoxides such as bis(4-hydroxyphenyl)sulfide andbis(4-hydroxyphenyl)sulfoxide,bis-(3,5-dibromo-4-hydroxyphenyl)sulfoxide, etc. A variety of additionaldihydric phenols are also available and are disclosed in U.S. Pat. Nos.2,999,835, 3,028,365, and 3,153,008, all of which are incorporatedherein by reference. It is, of course, possible to employ two or moredifferent dihydric phenols or a copolymer of a dihydric phenol withglycol or with hydroxy or acid-terminated polyester, or with a dibasicacid in the event a polycarbonate copolymer or interpolymer rather thana homopolymer is desired for use in the preparation of the polycarbonatepolymers of this invention. Also employed in the practice of thisinvention are blends of any of the above dihydric phenols, the preferreddihydric phenol is bisphenol-A. The polyfunctional organic compoundswhich may be included within the scope of this invention are set forthin U.S. Pat. Nos. 3,635,895 and 4,001,184, which are incorporated hereinby reference. These polyfunctional aromatic compounds contain at leastthree functional groups which are carboxyl, carboxylic anhydride,haloformyl or mixtures thereof. Examples of these polyfunctionalaromatic compounds include trimellitic anhydride, trimellitic acid,trimellityl trichloride, 4-chloroformyl phthalic anhydride, pyromelliticacid, pyromellitic dianhydride, mellitic acid, mellitic anhydride,trimesic acid, benzophenonetetracarboxylic acid,benzophenonetetracarboxylic anhydride, and the like. The preferredpolyfunctional aromatic compounds are trimellitic anhydride ortrimellitic acid or their haloformyl derivatives. Also included hereinare blends of a linear polycarbonate and a branched polycarbonate.

The carbonate precursor can be either a carbonyl halide or abishaloformate. The carbonyl halides include carbonyl bromide, carbonylchloride, and mixtures thereof. The bishaloformates suitable for useinclude the bishaloformates of dihydric phenols such asbischloroformates of 2,2-bis(4-hydroxyphenyl)propane,2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane, hydroquinone, and thelike, or bishaloformates of glycols such as bishaloformates of ethyleneglycol, and the like. While all of the above carbonate precursors areuseful, carbonyl chloride, also known as phosgene, is preferred.

By adding monofunctional compounds which are capable of reacting withphosgene or with the end groups of the polycarbonates consisting of thechlorocarbonic acid ester group and which terminate the chains, such asthe phenols, e.g., phenol, tertbutylphenyl, cyclohexylphenol, and2,2-(4,4-hydroxyphenylene-4'-methoxyphenylene)propane, aniline andmethylaniline, it is possible to regulate the molecular weight of thepolycarbonates.

As mentioned hereinabove, the acid acceptor is an alkali or alkalineearth metal hydroxide. Illustrative of these acid acceptors are sodiumhydroxide, lithium hydroxide, potassium hydroxide, calcium hydroxide andthe like. The amount of said acid acceptor present should be sufficientto maintain the pH of the aqueous caustic solution above about 9.

Illustrative of the inert organic solvents which are present during thereaction and which dissolve the polycarbonate as it is formed arearomatic hydrocarbons and halogenated hydrocarbons such as benzene,toluene, xylene, chlorobenzene, orthodichlorobenzene, chloroform,methylene chloride, carbon tetrachloride, trichloroethylene anddichloroethane. The solvent is present in an amount effective tosolubilize or dissolve substantially all of the polycarbonate as it isformed.

The catalytic compounds within the scope of the instant invention arethe nitrogen crown-cyclic compounds represented by the general formulae##STR3## wherein W, W¹, W², W³ and W⁴ are independently selected fromdivalent heteroorganic radicals containing at least 5 atoms, preferablyfrom 5 to about 14 atoms, selected from oxygen, nitrogen and carbon,with the proviso that for every one hetero atom, i.e., oxygen ornitrogen, present, there are present at least two carbon atoms. Thecarbon atoms present in W, W¹, W², W³ and W⁴ may be substituted withalkyl radicals, preferably alkyl radicals containing from 1 to about 20carbon atoms, or they may be part of an alicyclic or aromatic ring. Ifnitrogen atoms are present in W-W⁴, these nitrogen atoms may be, if theyhave an available bond, substituted with an alkyl radical, preferablyone containing from 1 to about 20 carbon atoms. R and R¹ in Formulae Iare independently selected from hydrogen and alkyl radicals, preferablyalkyl radicals containing from 1 to about 20 carbon atoms.

Illustrative examples of the nitrogen crown-cyclic compounds, sometimesalso referred to as crypts, represented by Formulae I and II include:##STR4##

For convenience, some of the nitrogen crown-cyclic catalysts of FormulaI and II are employed in the form of their mineral acid salts,preferably nitrate, nitrite, sulfate, sulfite, phosphate, phosphite,halide and hydrohalide salts.

Illustrative mineral acid salts of the nitrogen crown-cyclic compoundsof Formula I and II include: ##STR5##

The nitrogen crown-cyclic compounds represented by Formulae I and II areknown compounds whose chemistry and preparation are well known toworkers in the art. Thus, general methods of their preparation aredescribed by J. J. Christensen, D. J. Etough, and R. M. Izatt inChemical Reviews, Vol. 74, page 351 (1974).

The amount of the nitrogen crown-cyclic compound present during thereaction is a catalytic amount. By catalytic amount is meant an amounteffective to catalyze the reaction between the dihydric phenol and thecarbonate precursor to produce the polycarbonate. Generally, this amountranges from about 0.01 to about 10 weight percent based on the weight ofthe dihydric phenol present.

The process of the instant invention is carried out by reacting adihydric phenol, such as bisphenol-A, with a carbonate precursor, suchas phosgene, in a reaction medium containing an aqueous caustic solutionand an inert organic solvent for the polycarbonate and in the presenceof a catalytic amount of the nitrogen crown-cyclic compound of FormulaeI or II.

The temperature at which this reaction proceeds may vary from below 0°C. to about 100° C. The reaction proceeds satisfactorily at temperaturesranging from about room temperature (25° C.) to about 50° C. Since thereaction is exothermic, the rate of carbonate precursor addition may beused to control the reaction temperature. The amount of carbonateprecursor, such as phosgene, required will generally depend upon theamount of dihydric phenol present. Generally, one mole of the carbonateprecursor will react with one mole of dihydric phenol to provide thepolycarbonate. When a carbonyl halide, such as phosgene, is used as thecarbonate precursor, two moles of hydrohalic acid such as HCl areproduced by the above reaction. These two moles of acid are neutralizedby the alkali and alkaline earth metal hydroxide acid acceptor present.The foregoing are herein referred to as stoichiometric or theoreticalamounts.

PREFERRED EMBODIMENT OF THE INVENTION

In order to more fully and clearly illustrate the present invention, thefollowing examples are presented. It is intended that the examples beconsidered as illustrative rather than limiting the invention disclosedand claimed herein. In the examples, all parts and percentages are on aweight basis unless otherwise specified.

EXAMPLE 1

This example illustrates an unsuccessful attempt to prepare apolycarbonate polymer via the interfacial polymerization techniquewithout the presence of a catalyst. To a reactor fitted with a refluxcondenser and a mechanical agitator are charged 57 parts of2,2-bis(4-hydroxyphenyl)propane, 157 parts of water, 325 parts ofmethylene chloride, and 1.2 parts of para-tertiary-butylphenol. Phosgeneis then added to the reaction mixture at a rate of 0.65 parts per minutefor a period of 30 minutes while maintaining the pH at 9 by the additionof a 15% aqueous sodium hydroxide solution. After 30 minutes, the pH israised to 11.0 by the use of additional amounts of sodium hydroxidesolution. Phosgenation is continued for a further 10 minutes at this pH.The material is recovered from the reaction and found to have anintrinsic viscosity of 0.12 dl./g. This indicates that no practicaldegree of polymerization is achieved.

EXAMPLE 2

The procedure of Example 1 is substantially repeated, except that thephosgenation is carried out in the presence of 0.6 gram of2,2,5,9,9,11-hexamethyl-1,5,8,12-tetraaza-14-crown-4,11-dienedihydrobromide hydrate. The polycarbonate is recovered and is found tohave an intrinsic viscosity of 0.34 dl./g. This indicates the formationof a high molecular weight aromatic polycarbonate.

EXAMPLE 3

The procedure of Example 1 is substantially repeated, except that thephosgenation is carried out in the presence of 0.72 gram of1,10-dimethyl-1,10-diaza-4,7,13,16-tetraoxacyclooctadecane. Thepolycarbonate is recovered and is found to have an intrinsic viscosityof 0.56 dl./g. This value indicates the formation of a high molecularweight aromatic polycarbonate.

EXAMPLE 4

The procedure of Example 1 is substantially repeated, except that thepara-tertiarybutylphenol of Example 1 is replaced with an equivalentamount of phenol and the phosgenation is carried out in the presence of0.1 gram of 1,10-diaza-4,7,12,16,21,24-hexaoxabicyclo-[8.8.8]hexacosane.The polycarbonate is recovered and is found to have an intrinsicviscosity of 0.44 dl./g. This indicates the formation of a highmolecular weight aromatic polycarbonate.

EXAMPLE 5

The procedure of Example 4 is substantially repeated, except that thephenol chain terminator of Example 4 is omitted. The polycarbonate isrecovered and is found to have an intrinsic viscosity of 1.14 dl./g.This value is indicative of the formation of a very high molecularweight aromatic polycarbonate.

As can be seen by comparison of Example 1 with Examples 2-5, the use ofthe nitrogen crown-cyclic catalysts of the instant invention results inthe production of high molecular weight aromatic polycarbonates via theinterfacial polymerization technique, while in the absence of acatalyst, the interfacial polymerization technique is ineffective inproducing high molecular weight aromatic polycarbonates undersubstantially identical reaction conditions.

It will thus be seen that the objects set forth above, among those madeapparent from the preceding description, are efficiently attained, andsince certain changes may be made in carrying out the above process andthe composition set forth without departing from the scope of theinvention, it is intended that all matters contained in the abovedescription shall be interpreted as illustrative and not in a limitingsense.

What I claim is:
 1. An interfacial polymerization process for preparinghigh molecular weight aromatic polycarbonates which comprises reacting,under interfacial polycarbonate-forming conditions, a dihydric phenoland a carbonate precursor in the presence of a catalytic amount of acatalyst selected from the group consisting of nitrogen crown-cycliccompounds and mineral acid salts of nitrogen crown-cyclic compounds. 2.The process of claim 1 wherein said catalyst is a nitrogen crown-cycliccompound.
 3. The process of claim 2 wherein said nitrogen crown-cycliccompound is represented by the formula ##STR6## wherein R and R¹ areindependently selected from the group consisting of hydrogen and alkylradicals; and W and W¹ are independently selected from the groupconsisting of divalent heteroorganic radicals containing at least 5atoms selected from the group consisting of oxygen, nitrogen and carbon,with the proviso that for every hetero atom present, there are presentat least two carbon atoms.
 4. The process of claim 3 wherein at leastone carbon atom present in W or W¹ contains at least one alkylsubstituent thereon.
 5. The process of claim 3 wherein at least onecarbon atom present in W or W¹ is part of an alicyclic or aromatic ring.6. The process of claim 2 wherein said nitrogen crown-cyclic compound isrepresented by the general formula ##STR7## wherein W², W³ and W⁴ areindependently selectedfrom the group consisting of divalentheteroorganic radicals containing at least 5 atoms selected from thegroup consisting of carbon, nitrogen and oxygen, with the proviso thatfor every hetero atom present, there are present at least two carbonatoms.
 7. The process of claim 6 wherein at least one carbon atompresent in W², W³ or W⁴ contains at least one alkyl substituent thereon.8. The process of claim 6 wherein at least one carbon atom present inW², W³ or W⁴ is part of an alicyclic or aromatic ring.
 9. The process ofclaim 1 wherein said catalyst is a mineral acid salt of a nitrogencrown-cyclic compound.
 10. The process of claim 1 wherein said catalystis present in an amount of from about 0.01 to about 10 weight percentbased on the weight of said dihydric phenol.
 11. The process of claim 10wherein said dihydric phenol is bisphenol-A.
 12. The process of claim 11wherein said carbonate precursor is phosgene.